A vehicle air bag module is a complete air bag unit which is assembled apart from the vehicle and then coupled as a unit with the vehicle. Typically, an air bag module includes (i) a reaction device, (ii) a folded air bag connected to the reaction device, (iii) an inflator, or gas generator, connected to the reaction device, and (iv) a cover connected to the reaction device to complete an enclosure for the folded air bag. The module is generally coupled with a structural part of the vehicle via the reaction device. In the case of a passenger side air bag module, for example, the reaction device may be coupled with the support structure for the instrument panel of the vehicle. Alternatively, in the case of a driver side air bag module, the reaction device may be coupled with the steering wheel support structure.
When coupled with a vehicle, an air bag module operates to deploy an air bag at the onset of a vehicle collision. Specifically, at the onset of a collision, a chemical mixture in the inflator that forms part of the module is ignited to generate large quantities of gas under relatively high pressure. The gas simultaneously (i) forces the air bag through the cover and (ii) inflates the air bag. As the air bag is being inflated, relatively high forces are applied to the various components of the air bag module. The reaction device transmits such forces to the vehicle structure to stabilize the air bag module during deployment of the air bag.
Over the years, various techniques for forming air bag modules have been suggested. One well known technique comprises initially securing an air bag and an inflator with a reaction device, folding the air bag into a predetermined pattern relative to the inflator and the reaction device, and then attaching a cover to the reaction device. The reaction device is adapted to be coupled with a structural part of the vehicle, to couple the module with the vehicle. One example of such a technique is shown in U.S. Pat. No. 4,148,503, wherein an air bag module comprises an inflator and an air bag secured to a reaction device or bracket arranged at a central part of a steering wheel and secured to a steering wheel spoke. The air bag is arranged to surround the inflator and is then received in a folded condition within a receiving case or cover. Another example of such a technique is shown in U.S. Pat. No. 4,842,300, wherein an air bag module comprises an inflator and an air bag secured within a reaction device. The air bag is folded into a predetermined pattern within the reaction device relative to the inflator, and a cover is then attached to the reaction device to complete the module.
Another known technique for forming an air bag module is to initially form a subassembly comprising a reaction device, a folded air bag and a cover, and to secure an inflator to the subassembly to complete the module. The subassembly is formed by folding the air bag into a predetermined configuration, and securing and closing the air bag within a covered reaction device to complete the subassembly. The inflator is then secured to the subassembly to complete the air bag module. This technique minimizes the handling of inflators in assembling the module. Also, it enables inflators to be transported separately from the subassembly. Thus, if the chemical mixture in the inflators is accidentaly ignited during transport, the subassemblies of the modules are not destroyed. An example of such a technique is shown in U.S. Pat. No. 4,153,273.
As seen from the foregoing discussion, the reaction device performs several important functions in an air bag module. The reaction device connects the module to a structural portion of the vehicle and, during air bag bag deployment, transmits forces from the air bag module to the vehicle. Further, the reaction device is the element of the module to which virtually all other components of the module (i.e., inflator, air bag and cover) are connected. Thus, the reaction device integrates the other air bag module components into a structural unit.
In the air bag industry, new and useful techniques for forming air bag modules are becoming increasingly important. Air bag modules are currently being installed in large numbers of automobiles. The number of air bag modules installed in the future will continue to increase, as consumer demand and federal regulatory requirements for vehicle safety also continue to increase. To enable auto makers to meet this growing demand, there is a continuing need for simple and effective techniques which lend themselves to the mass production of air bag modules.
Applicants believe there is a continuing need for air bag module structures and assembly techniques which allow inflators to be manufactured and transported separately from the remaining parts of the modules, and incorporated into the modules as the last step in the assembly process. This minimizes the risk of damage to the remaining parts of the modules, due to accidental ignition of an inflator.